<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
.admin-sidebar-list > li input {
    position: absolute;
    width: 100%;
    height: 48px;
    z-index: 10;
    opacity: 0;
}

.admin-sidebar-list > li ul {
    margin: 0;
    list-style-type: none;
    padding-left: 20px;
    display: none;
}

.admin-sidebar-list > li input:checked ~ ul {
    display: block;
}
    </style>
</head>
<body>
<ul class="admin-sidebar-list">
    <li>
        <input type="checkbox" checked>
        <a>目录一</a>
        <ul>
            <li><a>子目录一</a></li>
            <li><a>子目录二</a></li>
        </ul>
    </li>
    <li>
        <input type="checkbox">
        <a>目录二</a>
        <ul>
            <li><a>子目录三</a></li>
            <li><a>子目录四</a></li>
        </ul>
    </li>
</ul>
</body>
</html>